A noninvasive, low-cost blood test was developed to help doctors diagnose some types of malignant childhood tumor (Br J Cancer. doi:10.1038/bjc.2015.429). The test could enable clinicians to monitor treatment effectiveness without exposing patients to repeated doses of radiation.

The test targets germ cell cancers. Germ cells are those cells that develop into sperm and egg cells. They can also develop into both benign and malignant tumors, particularly in the testes or ovaries, where the cells are normally found. However, occasionally germ cells can get trapped in the wrong part of the body during development and may later turn into brain tumors, for example.

The 5-year disease-free and overall survival rates for patients with high-risk malignant germ cell tumors is less than 50%; therefore, accurate diagnosis and monitoring is crucial to improving outcomes for patients. All of the current tests are expensive, and none are ideal.

Biopsy is the most reliable diagnostic method currently in use; however, they are prone to sampling errors and thereby may not be representative of the tumor as a whole. Computerized tomography (CT) scans and magnetic resonance imaging (MRI) provide useful information but are not diagnostic, and do not discriminate between benign and malignant tumors.

Although the ideal diagnostic tool would be a noninvasive blood test, currently available tests only identify approximately 3 in 5 malignant germ cell tumors, potentially delaying diagnosis and the ability to prioritize patients for surgery. Two in 5 patients are not candidates for disease monitoring via routine blood testing; these patients require follow-up CT scans, which include exposure to harmful radiation and an associated increased secondary cancer risk.

“Although relatively rare, childhood germ cell tumors need to be diagnosed accurately and followed up carefully to give us the best chances of treating them,” said Professor Nick Coleman, the Department of Pathology, University of Cambridge, United Kingdom. “At the moment, we are not good enough at diagnosing these tumors and monitoring their treatment: we need better, safer, and more cost-effective tests.”

In research funded by Sparks charity, Great Ormond Street Hospital Children’s Charity, and Cancer Research UK, researchers at the University of Cambridge developed a test for blood and cerebrospinal fluid samples that looks for a specific panel of 4 pieces of short genetic code (microRNAs) that are found in greater quantities in malignant germ cell tumors. The test can distinguish malignant germ cell tumors and those that are benign as well as other cancers. It can be used for diagnosis of malignant germ cell tumors in any part of the body, including the brain.

The test can also check treatment response. Its safety and cost-effectiveness allows for frequent testing for disease recurrence.